The present disclosure relates to a semiconductor device and is applicable, for example, to a semiconductor device having a self-diagnosis function.
Recently, ISO26262 set by the International Organization for Standardization has been collecting attention as a functional safety standard for in-vehicle electronic devices. Functional safety refers to securing minimum tolerable safety by implementing a functional measure, should any element of an in-vehicle electronic device, for example, a microcontroller develop a fault. In the ISO26262, requesting a high fault detection rate, in-vehicle microcontrollers incorporate a scan circuit for performing a built-in self-test (BIST). Generally, in a microcontroller, a BIST is performed during a period between after the microcontroller is powered on and before the microcontroller starts real operation (in-vehicle control such as engine control and brake control). The BIST performed in an in-vehicle microcontroller is required to achieve a high fault detection rate in a predetermined amount of time, so that the BIST when performed involves a high rate of current consumption variation. Generally, it is known that, when the rate of current consumption variation is high in a circuit, resonance noise is generated in the power supply line in the circuit. A method to reduce power supply resonance noise is disclosed in Japanese Unexamined Patent Application Publication No. 2009-188881 (patent document 1).